A number of investigators have suggested that lingual activity is often modified in the presence of palatopharyngeal incompetency or in some types of anterior malocclusions. Although most clinicians acknowledge the importance of lingual articulation in the production of speech, relatively few instrumental investigations have been performed. The development of instruments capable of precisely measuring pressure and airflow along the vocal tract now provides an opportunity to investigate lingual function in a quantitative way. The pressure-flow technique, developed in our laboratory, will be utilized in conjunction with palatographic and acoustic techniques to provide a dynamic analysis of lingual articulation under a variety of conditions. Normal and cleft palate subjects, as well as subjects with anterior malocclusion, will be studied in terms of lingual constrictions, lingual impedance to airflow, lingual placements, oral port size, palatopharyngeal orifice size, respiratory effort, the acoustic speech wave and intelligibility. Since so many parameters are involved, a laboratory computer will be used to store data, describe movement patterns and coordinate and align recordings of the resulting speech wave for eventual display. Point-by-point comparison of the acoustic wave form with the physiologic and aerodynamic parameters associated with sound productions should provide more definitive information on the role of the tongue in normal and disordered speech.